In recent years, digitalization has been remarkably propaganted also in the field of a color print using a color photographic paper. For example, a digital exposure system by laser scanning exposure has been rapidly spread in comparison with a conventional analog exposure system of directly conducting a printing from a processed color negative film using a color printer. The digital exposure system is characterized in that a high image quality is obtained by conducting image processing, and it greatly contributes to improvement of qualities of color prints using a color photographic paper. Further, along with the rapid propagation of digital cameras, it is also considered to be an important factor that a color print with a high image quality is easily obtained from these electronic recording media. It is believed that they will lead to further remarkable popularization.
As the silver halide emulsion for use in a color photoqraphic paper, a silver halide of a high silver chloride content has been used primarily because of a demand for rapid processing whereby productivity can be mainly enhanced. The silver halide emulsion of a high silver chloride content generally has a tendency to cause both low sensitivity and soft gradation enhancement upon a high illuminance exposure such as a laser scanning exposure. Therefore, various investigations to improve such problem have been conducted.
It has been known to dope iridium in order to improve a high illuminance reciprocity law failure of a silver chloride emulsion. However, it has been also known that the silver chloride emulsion with doped iridium causes latent image sensitization in a short time after exposure. For example, JP-B-7-34103 discloses that the problem of latent image sensitization can be overcome by providing a localized phase of high silver bromide content and doping iridium therein. The silver halide emulsion prepared by the afore-mentioned method shows high sensitivity and hard gradation, and does not cause the problem of latent image sensitization even upon a relatively high illuminance exposure of about 1/100 second. However, another problem has been found by further investigations that it is difficult to obtain hard gradation in a silver halide emulsion still providing high sensitivity even upon an ultra-high illuminance exposure of about 1μ second that is required in a digital exposure system using laser scanning exposure. For example, U.S. Pat. No. 5,691,119 proposes a method of further enhancing high illuminance gradation by preparing emulsion grains with a localized phase of high silver bromide content. However, this method has the disadvantages that an effect on the hard gradation enhancement is neither satisfactory nor photographic performance is stable in repeat of preparation.
For example, U.S. Pat. No. 5,783,378 proposes a method of reducing a high illuminance reciprocity law failure by using at least three kinds of dopants, resulting in hard gradation enhancement. However, the reason why hard gradation can be obtained resides in the use of a dopant acting as a desensitizing and hard gradation-enhancing agent. Therefore, this method is fundamentally incompatible with high sensitivity enhancement.
For example, U.S. Pat. No. 5,736,310 discloses that emulsions having high sensitivity and with a less reciprocity law failure upon high illuminance exposure can be obtained by emulsions containing I having a maximum concentration in a sub-surface of the high silver chloride emulsion. Indeed, along with the increase of illuminance for exposure, high sensitivity can be obtained using the emulsions. However, it has been found that the gradation is so soft that these emulsions are not suitable to digital exposure with a limited dynamic range in terms of light volume.
Further, for example, U.S. Pat. No. 5,399,475 discloses that high sensitivity can be obtained by localizing and incorporating a phase of a high silver bromide content in various forms into emulsion grains of a high silver chloride content.
On the other hand, regarding the color printing system, techniques such as an ink jet system, a sublimation system and a color xerography system have been progressed respectively and accepted as the color printing methods providing an excellent photographic image quality. Among them, the feature of the digital exposure system using the color photographic paper resides in the high image quality, high productivity and high fastness of images. It is desired to further improve these performances and show photographs with higher quality, more readily and economically.
Particularly, if it is possible to receive recording media of digital camera at a shop counter, finish a high quality print in a short period of time of about several minutes and return the same in situ, that is, if one stop service for color printing is possible, superiority of color printing using a color photographic paper is increased much more. Further, if rapid processability of the color photographic paper is improved, a printing equipment of high productivity even with a smaller size and a low price can be used and popularization of the one stop service for a color print can be expected much more. In view of the above, it is particularly important to improve the rapid processability of the color photographic paper.
For enabling one-stop service for color printing using a color photographic paper, it is necessary to study on various view points such as shortening of exposure time, shortening of so-called latent image time from exposure to the start of the processing and shortening of the time from processing to drying, and various proposals have hitherto been made with respect to the individual point set forth above.
Among them, in a case where a time required for exposure per one sheet of print is extremely shorter compared with other systems and a printer has a performance of ordinary printers used in the shop, no substantial problem occurs. A printer has already been designed so as to make the latent image time as short as possible. Further, shortening of the time from processing to drying has also hitherto been made. Further, various means for rapid processing have been proposed, for example, by improving the compositions of the processing solution or processing temperature or stirring conditions for the processing solution, squeeze of the light-sensitive material, and the drying method.
From the above view, the present inventors have made studies on the color development of a color photographic paper for a short time of 28 sec. or lass from both sides of a processing formula and a processing step. However, they failed to solve the problem that the maximum density cannot be attained within such short period of processing time, so long as a conventional color photographic paper is employed.
On the other hand, from the viewpoint of further enhancing superiority of the print obtained by a conventional silver salt-using color photographic paper to the afore-mentioned new color print systems, a demand for reduction in cost of the color photographic paper is increasing more than before. As a means to respond to the demand, it has been considered to provide a color photographic paper for a common use of digital/analogue that is employed for both a digital exposure system and an analogue exposure system respectively. However, it is fairly difficult to obtain a satisfactory performance by the afore-mentioned color photographic paper because there is a definite difference in exposure time between these systems, and in addition reciprocity law failure characteristics and latent image stability. In such circumstances, it has been desired more and more to develop a light-sensitive material with a less difference in photographic performance such as reciprocity law failure and latent image stability, obtained by digital exposure and analogue exposure.
In recent years, in the field of photographic processing services, a photographic light-sensitive material that can be processed rapidly and form a high-quality image is demanded as part of improvement of service to users and as means for improving productivity. To respond to this demand, currently, a rapid processing is usually carried out in which a photographic light-sensitive material containing a high silver chloride emulsion (hereinafter, also referred to as “high silver chloride printing material”) is processed in 45 seconds for a color developing time, and in about 4 minutes for a total processing time of from the start of the developing step to the completion of the drying step (for example, Color Processing CP-48S (trade name) or the like, manufactured by Fuji Photo Film Co., Ltd.). However, as compared with the rapidity of making images by other color image making methods (for example, an electrostatic transfer method, a thermal transfer method, an ink jet method), it cannot be said that even this rapid development processing system for high silver chloride printing materials shows a satisfactory rapidity. For this reason, there are demands for a super(ultra)-rapid processing, of which the total processing time from the start of development and the completion of drying of a high silver chloride color printing material, is on the level of about 1 to 2 minutes.
As a means of improving an ultra-rapid processing suitability, it has been considered to reduce a coating amount of organic materials and a coating amount of a hydrophilic binder by employment of a highly active coupler or a coupler capable of providing a large molecular extinction coefficient of a colored dye, and/or to employ a silver halide emulsion that can be rapidly developed. For example, JP-A-3-21947 proposes to set a limitation in terms of a coating amount of a hydrophilic colloid. However, these means are insufficient in terms of compatibility of digital exposure suitability with suitability of ultra-rapid processing which indicates that a total processing time of from start of development up to completion of drying is a level of 1 to 2 minutes.
The present inventors have made intensive studies, and tried to employ a silver halide emulsion comprising silver halide grains containing 90 mole % or more of silver chloride and having both a silver bromide-containing phase and a silver iodide-containing phase each formed in the layer state in the grains for a light-sensitive material containing a hydrophilic binder (colloid) in less than a normal coating amount. However, in this case, unexpected results (phenomena) were found that pressure-sensitized streaks in the yellow color appeared to cause a problem.
In the case where a color photographic paper is subjected to digital exposure by a laser scanning exposure, it is preferable that the color photographic paper has a moderate gradation. That is, if the contrast (gradation) is too high (hard), uneven color such as banding and shading easily occurs and the detail tone at the highlight of a picture tends to disappear. In contrast, if the contrast is too low (soft), it becomes difficult to cover a reproduction region from the end of toe to a high density within a dynamic range of luminous intensity of laser light sources.
For enabling one stop service for color printing using a color photographic paper, it is necessary to study on various view points such as shortening of exposure time, shortening of so-called latent image time from exposure to the start of the processing and shortening of the time from processing to drying, and various proposals have hitherto been made with respect to the individual point set forth above.
Among them, in a case where a time required for exposure per one sheet of print is extremely shorter compared with other systems and a printer has a performance of ordinary printers used in the shop, no substantial problem occurs. A printer has already been designed so as to make the latent image time as short as possible. Further, shortening of the time from processing to drying has also hitherto been made. Further, various means for rapid processing have been proposed, for example, by improving the compositions of the processing solution or processing temperature or stirring conditions for the processing solution, squeeze of the light-sensitive material, and the drying method.
From the above view, the present inventors have tried to color develop a color photographic paper for a short time of 28 sec. or less after the short latent image time of 9 sec. or less. However, it has been found that if a mixture of two kinds of emulsions whose sensitivities are made different by a different grain size is used in the same color-developable layer, a color density particularly at the shoulder portion of the characteristic curve is significantly changed by a fluctuation in the composition of a color developing solution, resulting in making it difficult to obtain a print with a stable performance. Further, it has been found that the instability of performance is remarkable upon a laser scanning exposure. As a result of various studies about resolution of the afore-mentioned problem, the present inventors have found that the problem can be overcome by employing a silver halide emulsion layer containing a mixture of at least two different kinds of emulsions at least one of which contains a particular metal complex.
JP-A-10-307364 discloses photographic elements composed of a photographic emulsion comprising at least two different kinds of emulsions each containing the same silver halide grains, except that the grains of at least one emulsion are treated with a compound capable of lowering sensitivity. As the compound capable of lowering sensitivity, a particular disulfide compound is described. It is also disclosed that the use of the compound enables to readily prepare a plurality of emulsions with a different sensitivity from each other, and to lessen the amounts of sensitizing dyes and agents for chemical sensitization compared with a low sensitive emulsion prepared by the use of small size grains, thereby reducing a cost.
JP-A-3-192346 and JP-A-3-241342 disclose to use a mixture of emulsions different in a content of iridium by 40% or more. It is described that a mixture of the emulsions enables to form images such that a fluctuation in sensitivity and gradation resulting from a change of exposure illuminance is reduced.
However, regarding the color photographic paper, if it is stored in the state of the light-sensitive material before exposure, a fog density of the yellow dye-developable layer in particular tends to increase so easily that a white ground after exposure and processing sometimes deteriorates particularly in the yellowish direction. In other color printing systems such as ink jet and color xerography, an ink or toner is laid on an only image portion, so that a quality of the white ground essentially depends on the whiteness of a support. Accordingly, a problem of fogging resulting from storage is one of subject matters necessary to be improved in the color photographic paper. As a result of our investigations, it has been made clear that the deterioration of white ground results from fogging of an emulsion by the action of natural radiation. Besides, it is important to minimize fluctuation in photographic performance resulting from a change of processing factors in order to stabilize and uniform a coloring density of a color photographic paper. The photographic performances to be improved in particular are a so-called “back contamination” that is a technical term employed to indicate an increase of density resulting from a mixing of a bleach-fixing solution in a color developing solution, as well as a “squeegeeing unevenness” resulting from a squeegeeing inadequacy between a color developing solution and a bleach-fixing solution. Particularly when a rapid processing is carried out, a processing dependency of these adverse performances sometimes increases. Therefore, it is very important to improve these adverse performances thereby obtaining a stable and uniform coloring. Accordingly from the viewpoints of overcoming week points compared to competing printing systems thereby enhancing superiority of the color photographic paper, it is important to improve deterioration of a white ground resulting from storage of the color photographic paper in the state of a light-sensitive material before exposure as well as a change or unevenness of the coloring density resulting from fluctuation in processing factors.
Usually, as a silver halide emulsion for use in a color photographic paper, a silver halide emulsion of a high silver chloride content is used from a demand for rapid processability. It has been known to incorporate various metal complexes in the silver halide emulsion of a high silver chloride content. Further, it has been known to dope an Ir complex in order to improve high illuminance reciprocity law failure of a silver chloride emulsion and in order to obtain high contrast gradation even upon a high illuminance (exposure). For example, JP-B-7-34103 discloses that the problem of latent image sensitization is overcome by providing a localized phase of a high silver bromide content and doping an Ir complex therein. U.S. Pat. No. 4,933,272 discloses that the low illuminance reciprocity law failure can be decreased by incorporating a metal complex containing NO or NS in a ligand. U.S. Pat. Nos. 5,360,712, 5,457,021, and 5,462,849 disclose that the reciprocity law failure can be decreased by incorporation of metal complexes comprising specified organic ligands. U.S. Pat. Nos. 5,372,926, 5,255,630, 5,255,451, 5,597,686, 5,480,771, 5,474,888, 5,500,335, 5,783,373 and 5,783,378 disclose that the performance such as the reciprocity law failure characteristic of the emulsion of a high silver chloride content can be improved by the combination of an Ir complex or a metal complex containing NO as a ligand. JP-A-2000-250156, JP-A-2001-92066 and JP-A-2002-31866 disclose a technique of producing an emulsion providing excellent latent image stability after exposure by the combination of an Ir complex and a Rh complex.
Further, JP-A-58-95736, JP-A-58-108533, JP-A-60-222844, JP-A-60-222845, JP-A-62-253143, JP-A-62-253144, JP-A-62-253166, JP-A-62-254139, JP-A-63-46440, JP-A-63-46441, JP-A-63-89840, U.S. Pat. Nos. 4,820,624, 4,865,962, 5,399,475, and 5,284,743 disclose that high sensitivity can be obtained by localization and incorporation of a phase of high silver bromide content in various forms into an emulsion of high silver chloride content.
Further, U.S. Pat. Nos. 5,726,005 and 5,736,310 disclose that emulsions with high sensitivity and less high illuminance reciprocity law failure can be obtained by emulsions containing I (band) having a maximum density in the sub-surface of the silver chloride emulsion. European Patent (EP) No. 0,928,988A disclose in the example that the emulsions excellent in reciprocity law failure, temperature dependence upon exposure or pressure property can be obtained by incorporation of a specified compound in the grains having I band formed at the 93% step of grain formation.
However, the known techniques described above do not mention the improvement in the photographic characteristic at carrying out the color-develop step within 28 sec. In detail, these known techniques do not disclose that the use of at least two emulsions containing a particular metal complex will improve the instability of photographic performances in the case where after a short latent image time of 9 sec. or less, color development is carried out within a short time of 28 sec., even though a moderate gradation can be obtained upon a digital exposure by a laser scanning exposure.
Further, these known technical reports are silent in a silver halide color photographic light-sensitive material with deterioration of a white ground resulting from storage of the color photographic paper being lessened even for a long period of time, and capable of providing the maximum density upon a rapid color development in a short period of time as well as a stable photographic performance against a fluctuation in the processing factors.